The present invention relates to medical stents and related methods. More specifically, the invention relates to medical stents having one end section which is softer than a section at the other end of the stent.
Fluid sometimes needs to be drained from a body. For example, urine formed in one or both kidneys might need to be drained into the bladder. One way to accomplish such drainage is to use a medical device that conveys the fluid (e.g., urine) through a lumen. Such devices include stents and catheters. Existing stents can be uncomfortable for the patient, especially when they reside in the ureter between the kidney and the bladder, or can be difficult for a medical professional to place in a patient.
The present invention provides medical stents for facilitating drainage of fluid and methods for placing such stents. For example, such stents can be placed in a ureter to facilitate drainage of fluid from a patient""s kidney to a patient""s bladder. Generally, stents according to the invention have a xe2x80x9csofterxe2x80x9d end and a xe2x80x9charderxe2x80x9d end. The harder end generally resides in the patient""s kidney while the softer end generally resides in the patient""s bladder. The harder end transitions to the softer end in a transition section produced by a co-extrusion process where deposition of a first material is gradually ceased and deposition of a second is gradually increased. The harder end is suited to retain the stent in the patient""s kidney and/or facilitate placement in a patient while the softer end is suited to increase patient comfort and/or, to a degree, retain the stent in the patient""s bladder. Such stents also are useful in other situations such as biliary drainage or, generally, where one body structure is drained to another body structure.
In one embodiment, a medical stent includes a single-piece, extruded stent body which does not substantially soften when exposed to a temperature of a human body. At least a portion of the stent body can be sized for placement in a ureter, and at least a section of the stent body can define holes therethrough. The stent body itself includes a first section, a second section, and a third section defining a lumen and located between the first and second sections. The first section includes a first material having a first durometer value while the second section includes a second material having a second durometer value. The second durometer value is greater than the first durometer value. The third section includes a co-extrusion of the first and second materials that is disposed between the first coil and the second coil. The first section defines a lumen and includes a first coil completing at least one revolution, and the second section defines a lumen and includes a second coil completing at least one revolution. An outer surface of the third section smoothly transitions to outer surfaces of the first and second sections immediately proximate the third section, and an inner diameter of the third section is substantially constant through the third section and on either side of the third section immediately proximate to the third section in the first and second sections.
The embodiment described above, or those described below, can have any of the following features. The first material can include ethylene vinyl acetate. The stent body can include a mark on an outer surface of the stent body. The stent body can include a radiopaque marking. The stent can have an outer diameter of about 4 French to about 9 French. The stent can have an inner diameter of about 0.38 inches. The stent can have a length of about 10 cm to about 30 cm as measured between the coils. The stent can include a hydrophilic coating. The first material can have a durometer value of about 70 to about 90 on a Shore A scale. The second material can have a durometer value of about 80 to about 95 on a Shore A scale. At least one of the coils can be asymmetric. An end of at least one of the first section and the second section can be tapered. A cross-section of the lumen in at least one of the first, second, and third sections can be circular. A cross-section of at least one of the first, second, and third sections can be circular. At least one of the first, second, and third section can include a radiopaque material.
In another embodiment, a medical stent includes a single-piece, extruded stent body which does not substantially soften when exposed to a temperature of a human body. At least a portion of the stent body can be sized for placement in a ureter, and at least a section of the stent body can define holes therethrough. The stent body itself includes a first section, a second section, and a third section defining a lumen and located between the first and second sections. The first section defines a lumen and includes a first coil completing at least one revolution, and the second section defines a lumen and includes a second coil completing at least one revolution. The first section includes a first material, and the second section includes a second material. The first coil has a first retention strength, and the second coil has a second retention strength. The second retention strength is greater than the first retention strength. The third section includes a co-extrusion of the first and second materials that is disposed between the first coil and the second coil. An outer surface of the third section smoothly transitions to outer surfaces of the first and second sections immediately proximate the third section. An inner diameter of the third section is substantially constant through the third section and on either side of the third section immediately proximate to the third section in the first and second sections.
In another aspect of the invention, a method for placing a medical stent includes inserting a medial stent, including any of the stents described above or below with any of the features described above or below, into a ureter.